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River floods and storms that send water surging through swamps and marshes near rivers and coastal areas might cut in half the average greenhouse gas emissions from those affected wetlands, according to recent research at Ohio State University. A study suggests that pulses of water through wetlands result in lower average emissions of greenhouse gases over the course of the year compared to the emissions from wetlands that receive a steady flow of water.

The study compared the emission of methand from wetlands under two different conditions, one with a pulsing hydrology system designed to resemble river flooding and one with a steady, low flow of water. The research showed that in areas of deeper water within the wetlands, methane gas fluxes were about twice as high in steady-flow systems than they were in pulsing systems. Methane emissions from edge zones, which are sometimes dry, were less affected by the different types of conditions.

Methane is the major component of natural gas and is a greenhouse gas associated with global warming. While the Environmental Protection Agency estimates that human activities are responsible for about 60 percent of methane emissions worldwide, wetlands are among the natural sources. Bacteria that produce methane during the decay of organic material cause wetlands to release the gas into the atmosphere.

The study by Ohio State University scientists is part of ongoing research comparing pulsing vs. steady-flow conditions in two experimental wetlands on the Columbus campus.

"Pulsing refers to a number of different conditions in wetlands – river pulses that happen on a seasonal basis, two-per-day coastal tides, and the rare but huge ones, like hurricanes or tsunamis," said William Mitsch, the study's senior author and director of the